Chronic fatigue/pain (CFS) patients reported frequent gastrointestinal symptoms (irritable bowel, constipation, abdominal pain, diarrhea, nausea) suggesting the possibility of an altered microbial flora in the gastrointestinal tract. The aim of this investigation is to determine if there is a change in the microbial intestinal flora of patients with CFS, and what causative factors may be implicated for these changes. Faecal samples from 27 polysymptomatic CFS patients and four age and sex matched control subjects were studied. Quantitative bacteriology of three aerobes (Escherichia coli, Klebsiella/Enterobacter group, and Enterococcus faecalis) and three anaerobes (Bacteroides spp., Bifidobacterium spp and Lactobacillus spp.) was performed on all samples. The mean distribution of E.coli as percentage of the total aerobic microbial flora for the control subjects and CFS patients was 92.3% and 49% respectively; Klebsiella/Enterobacter group, 0% and 3%; Enterococcus spp., < 1% and 24%. For the anaerobes, the mean percentage distribution of Bacteroides spp. for the control subjects and CFS patients was 92.8% and 91% respectively; Bifidobacterium spp, 7.1% and 2%; Lactobacillus spp., < 1% and 0%. The incidence of CFS patients with faecal E.coli greater than the percentage mean of control subjects was significantly different to that of the Bacteroides spp. (7 vs 21 respectively, p=0.0001) suggesting the possibility of an antimicrobial interaction among bacterial species.

Metabolites of Bacteroides spp. (lactic, propionic and butyric acids) were examined for growth inhibitory properties against three clinical faecal coliform ( E.coli, Klebsiella penumoniae and Proteus mirabilis). All three coliforms were susceptible to the three short chain fatty acids at pH3-4. At pH6-7 the three coliforms were not susceptible to lactic acid, partially to propionic acid, and fully to butyric acid. This study reported the marked alteration of the coliforms and lactic acid bacteria in the faecal microbial flora of CFS patients and that these changes may be related to inter-microbial activities among organisms.